This invention relates to improvements in flexible plastic film bags and more particularly to improved fasteners therefor which protect the contents and feature unique features for protecting the contents and eventually opening the bag.
In the development of closures for flexible film plastic bags, an important basic discovery has involved a mechanically closable rib and groove element. These rib and groove elements may take various shapes and with the various shapes, different physical advantages and features are achieved. One of the important advantages of a rib and groove type of closure is that it provides a convenient way of sealing a bag in that most rib and grooves when joined provide a moisture and air tight seal. A further feature is that a rib and groove arrangement can be relatively easily closed so that the bag can be filled and closed merely by applying mechanical closing pressure to force the rib element into the groove element. In the generic reference to rib and groove closure elements, it is recognized that there are many shapes and forms and the ribs and grooves are provided in single or multiple numbers and the present invention is not limited to one particular design but incorporates various designs having the physical characteristics which will be described herein.
For plastic bags handling various commodities including foodstuffs, it is advantageous to provide tamper-proof or tamper-evident features. That is, it is desirable to have a fastener which can contain material such as foodstuffs whereby the customer cannot open the bag or if opened, that it will be evident from viewing the bag that it has been opened and tampered with.
It is recognized that the art heretofore has included structures employing rib and grooves which when interlocked, they cannot be separated by pulling apart on the webs, as is disclosed for example in U.S. Pat. No. 3,808,649 issued to Steven Ausnit on May 7, 1974.
It is accordingly an object of the invention to provide a new and unique top fastener for a flexible plastic film bag employing an interlocking rib and groove but being manually unopenable by the usual manual external separation of the rib and groove.
A further object of the invention is to provide an easy open improved top fastener for a flexible plastic film bag which has tamper-evident features so that a previous unauthorized partial opening of the bag is evident by a visual inspection.
In accordance with the principles of the invention, a feature is to provide a rib and groove closure for the top of a flexible plastic film bag which has the advantage of readily being closed after filling and where the rib and groove would normally be separable manually except that the structure is provided so that no manual way is available to apply a lateral separating force transverse of the rib and groove fastener, and there are either no separation flaps extending above the rib and groove or only one so that the rib and grooves cannot be pulled apart.
A further feature of the invention is to provide a rib and groove fastener for the top of a flexible plastic film bag to afford the advantage of normal closing but wherein the rib and groove cannot be manually separated once closed and where the bag has to be opened by tearing a strip from the top of the bag.
A further feature of the invention is to provide a closable rib and groove element to close the top of a plastic film bag wherein the walls of the bag are perforated or spot joined beneath the fastener and are separable with a force less than that required to separate the rib and groove elements by a twisting or by longitudinally moving one profile against the other in opposing directions.
In summary, a feature of the invention is to provide a bag which, after it has been loaded, and the profiles closed and upper flanges either removed or omitted, the bag cannot be opened through the use of normal opening forces. There are no flanges or lips to provide such normal opening forces. Also, to provide a bag wherein if the fastener is subjected to other abnormal forces, such as twisting or driving one part of the fastener against the other in opposing directions, such forces will cause a tear line below the fastener to yield before the fastener will open. The fastener is not openable from above the profile and is not openable from below the profile.
Other advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which: